Some semiconductor processing tools feature multiple processing chambers that are arranged around a central hub chamber that houses one or more robot arms that may be used to transfer semiconductor wafers from a one of the processing chambers, into the hub chamber, and then into another processing chamber. Such hub chambers are typically referred to as “transfer modules,” and may also be connected with other types of chambers, e.g., load locks, furnaces, etc. Transfer modules are frequently designed to have radial symmetry, thus allowing the robot arm length to be minimized and allowing for the arm, in some configurations, to be able to be rotated 360° within the transfer module without colliding with anything.
In some semiconductor processing tools, the transfer module may be held at vacuum or near-vacuum conditions during normal operation; such transfer chambers are referred to as “vacuum transfer modules” (“vacuum transfer chamber” and “vacuum transfer module” are used herein in a generally interchangeable manner, and reference to one is to be understood to also include reference to the other). Such vacuum transfer modules may be hermetically sealed and may utilize special robots referred to as vacuum robots (or vacuum robot arms) that utilize special rotational joints, such as rotational joints having ferrofluidic seals, that permit rotational movement of the robot arm segments while preventing fluids from being sucked into the vacuum transfer module through such rotational joints. In order to provide for a vacuum-tight seal between such vacuum robots and the vacuum transfer chamber, such vacuum robots are typically bolted directly to the underside of the housing of the vacuum transfer chamber by way of a circumferential flange with some form of mechanical seal sandwiched between the flange and the underside of the housing.